Optical network unit reset message

ABSTRACT

A low-level reset message having a reset level provides a mechanism for an optical line terminal (OLT) to remotely reset a dysfunctional optical network unit (ONU). The reset message includes a reset level field which allows the OLT to instruct the ONU to perform a reset of some or all of its hardware and software components.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Patent Application No.62/352,888, which is titled “Optical Network Unit (ONU) Reset Message,”which was filed on Jun. 21, 2016, and which is incorporated by referencein its entirety.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not applicable.

REFERENCE TO A MICROFICHE APPENDIX

Not applicable.

BACKGROUND

Passive optical networks (PONs) may provide network services such asvoice, Internet, and video services to homes and businesses. In aconventional PON 100, shown in FIG. 1, optical line terminal (OLT) 110(typically located in a service provider's central office) communicateswith optical network unit (ONU) 120 (also referred to as an opticalnetwork terminal (ONT)). ONU 120 is typically located on the end-user'spremises. OLT 110 and ONU 120 communicate using, among other things,physical layer operations, administration, and maintenance (PLOAM)messages 130 and ONT management and control interface (OMCI) messages140. OMCI messages 140 are defined by Recommendation ITU-T G.988 andgenerally address ONU configuration, fault management and performancemanagement for optical access system operation. PLOAM messages 130 aredefined in Recommendations ITU-T G.987.3 and G.989.3 and generallyaddress low-level negotiations between an OLT and an ONU. PLOAM messages130 can be supported in low-level firmware, if not actually in hardware,and as such, they can be used even when an ONU is incapable ofcommunicating using higher level OMCI messages 140.

Under normal operations, service provider personnel may remotelyconfigure and troubleshoot an ONU, using OMCI messages 140. Serviceprovider personnel may even instruct an ONU to reset itself using OMCImessages 140. However, there are certain fault conditions when the ONUis unable to process incoming OMCI messages 140. In such conditions, theonly alternative is to restart the ONU manually, which requires eitheran in-person visit by the service provider's field support technician orelse an attempt, over the phone, to guide an untrained customer throughthe ONU reset process.

SUMMARY

In an embodiment, an ONU comprises a memory configured to store amanagement information base (MIB), low-level software, and high-levelsoftware, a PON interface configured to communicate using PLOAMmessages, and a processor coupled to the memory and the PON interface.The processor is configured to execute the low-level software andhigh-level software, receive a PLOAM reset message comprising a resetlevel, with the reset level comprising an indication of a component ofthe ONU to be reset, and reset the ONU according to the reset level. Insome embodiments, the reset level comprises an instruction for the ONUto reset the processor, the memory, and the PON interface, and with theprocessor further configured to reset the processor, the memory, and thePON interface and restart the low-level software and high-levelsoftware. In some embodiments, the reset level comprises an instructionfor the ONU to reset the low-level software and the high-level softwareand with the processor further configured to restart the low-levelsoftware and the high-level software. In some embodiments, the resetlevel comprises an instruction for the ONU to reset the high-levelsoftware and with the processor further configured to restart thehigh-level software. In some embodiments, the reset level comprises aninstruction for the ONU to reset the MIB and with the processor furtherconfigured to reset the MIB. In some embodiments, the PLOAM resetmessage comprises an instruction for the ONU to preserve the MIB beforeresetting the ONU and with the processor further configured to preservethe MIB before resetting the ONU and restore the MIB after resetting theONU. In some embodiments, the ONU comprises a current operating state,wherein the PLOAM reset message comprises a conditional resetinstruction or an unconditional reset instruction, wherein theconditional reset instruction comprises an indicator of an ONU operatingstate, and with the processor configured to reset the ONU when the PLOAMreset message comprises the conditional reset instruction and when thecurrent operating state corresponds to the indicator of the ONUoperating state, and reset the ONU when the PLOAM reset messagecomprises the unconditional reset instruction.

In an embodiment, an ONU receives and processes a PLOAM reset message byreceiving the PLOAM reset message comprising a reset level, with thereset level comprising an indication of a component of the ONU to bereset, and resetting the ONU according to the reset level. In someembodiments, the ONU comprises hardware, low-level software, andhigh-level software, wherein the reset level comprises an instructionfor the ONU to reset the hardware, the low-level software, and thehigh-level software, and further comprising resetting the hardware, thelow-level software, and the high-level software. In some embodiments,the ONU comprises low-level software and high-level software, whereinthe reset level comprises an instruction for the ONU to reset thelow-level software and the high-level software, and further comprisingresetting the low-level software and the high-level software. In someembodiments, the ONU comprises high-level software, wherein the resetlevel comprises an instruction for the ONU to reset the high-levelsoftware, and further comprising resetting the high-level software. Insome embodiments, the ONU comprises a MIB, wherein the reset levelcomprises an instruction for the ONU to reset the MIB, and furthercomprising resetting the MIB. In some embodiments, the ONU comprises aMIB, wherein the PLOAM reset message further comprises an instructionfor the ONU to preserve the MIB before resetting the ONU, and furthercomprising preserving the MIB before resetting the ONU and restoring theMIB after resetting the ONU. In some embodiments, the ONU comprises acurrent operating state, wherein the PLOAM reset message furthercomprises a conditional reset instruction or an unconditional resetinstruction, wherein the conditional reset instruction comprises anindicator of an ONU operating state, and further comprising resettingthe ONU when the PLOAM reset message comprises the conditional resetinstruction and when the current operating state corresponds to theindicator of the ONU operating state and resetting the ONU when thePLOAM reset message comprises the unconditional reset instruction.

In an embodiment, an OLT comprises a memory configured to store identityand state information about an ONU, a PON interface configured tocommunicate with the ONU using PLOAM messages, and a processor coupledto the memory and the PON interface. The processor is configured tocreate a first PLOAM reset message comprising a first reset level, withthe first reset level comprising an indication of a component of the ONUto be reset, and send the first PLOAM reset message to the ONU via thePON interface. In some embodiments, the first reset level comprises aninstruction for the ONU to reset hardware, low-level software, andhigh-level software associated with the ONU, an instruction for the ONUto reset low-level software and high-level software associated with theONU, an instruction for the ONU to reset high-level software associatedwith the ONU, or an instruction for the ONU to reset a MIB associatedwith the ONU. In some embodiments, the processor is further configuredto, prior to creating the first PLOAM reset message, detect that the ONUis not responding to OMCI messages and after sending the first PLOAMreset message, to detect that the ONU is still not responding to OMCImessages, create a second PLOAM reset message comprising a second resetlevel that is different from the first reset level, and send the secondPLOAM reset message to the ONU via the PON interface.

In an embodiment, an OLT resets a remote ONU by creating a PLOAM resetmessage comprising a first reset level, with the first reset levelcomprising an indication of a component of the ONU to be reset, andsending the first PLOAM reset message to the ONU via a PLOAM channel. Insome embodiments, the first reset level comprises an instruction for theONU to reset hardware, low-level software, and high-level softwareassociated with the ONU, an instruction for the ONU to reset low-levelsoftware and high-level software associated with the ONU, an instructionfor the ONU to reset high-level software associated with the ONU, or aninstruction for the ONU to reset a MIB associated with the ONU. In someembodiments, prior to creating the first PLOAM reset message, the ONU isfurther configured to detect that the ONU is not responding to OMCImessages and after sending the first PLOAM reset message, detect thatthe ONU is still not responding to OMCI messages, create a second PLOAMreset message comprising a second reset level that is different from thefirst reset level, and send the second PLOAM reset message to the ONUvia the PLOAM channel.

These and other features will be more clearly understood from thefollowing detailed description taken in conjunction with theaccompanying drawings and claims.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of this disclosure, reference is nowmade to the following brief description, taken in connection with theaccompanying drawings and detailed description, wherein like referencenumerals represent like parts.

FIG. 1 shows a conventional configuration of an ONU and an OLT.

FIG. 2 shows a hardware configuration suitable for use in implementingembodiments of the present disclosure.

FIG. 3 shows an embodiment of a PLOAM reset message according to anembodiment of the present disclosure.

FIG. 4 shows a flowchart for preparing and sending a PLOAM reset messageaccording to an embodiment of the present disclosure.

FIG. 5 shows a flowchart for processing receipt of a PLOAM reset messageaccording to an embodiment of the present disclosure.

DETAILED DESCRIPTION

The embodiments of this disclosure are directed at remotely resetting anONU using a PLOAM message. The disclosed PLOAM reset message includes areset level indicator, allowing service provider personnel to specify anoperation level, which may, for example, distinguish between a coldreset and a warm reset. A low-level reset message having a reset levelprovides a mechanism for an optical line terminal (OLT) to remotelyreset a dysfunctional optical network unit (ONU). The reset messageincludes a reset level field which allows the OLT to instruct the ONU toperform a reset of some or all of its hardware and software components.A capability is provided for remotely rebooting an ONU when the ONU isincapable of processing an OMCI reset request message. Embodiments ofthe present disclosure include a PLOAM reset message suitable forresetting an ONU according to a requested reset level, together withexamples of how an ONU may process the reset message. The disclosedembodiments allow service provider personnel to remotely reboot an ONUwhen the ONU is incapable of processing an OMCI reset request message.

FIG. 2 shows a hardware configuration for network device 200 which maybe suitable for use as ONUs and/or OLTs according to embodiments of thepresent disclosure. Network device 200 in the embodiment shown includesprocessor 230 coupled to network interface 210, network interface 220,and memory 240. Network interface 210 connects network device 200 to aPON, and as such, network interface 210 can comprise an opticalinterface. Network interface 220 connects network device 200 to anothernetwork or networks. When network device 200 is an OLT, this othernetwork may be the Internet or another service provider network, forexample. When network device 200 is an ONU, this other network may bethe customer's local area network, for example. In either case, networkinterface 220 may an electrical or optical network interface. By way ofexample and not limitation, processor 230 may be implemented as one ormore central processing units, microcontrollers, application-specificintegrated circuits, and/or other similar components, includingcombinations.

Processor 230 is also coupled with memory 240, which may includeinstructions for PLOAM module 242, OMCI module 244, and other programs246, together with associated configuration data 248 and transient data250. By way of example and not limitation, memory 240 may be implementedas random access memory, read-only memory, flash memory, disk-basedstorage, or the like, including combinations. When network device 200 isan ONU, configuration data 248 may include a MIB. When network device200 is an OLT, configuration data 248 may include identification andstate information about the ONUs that are connected to the OLT. Whennetwork device 200 is implemented as multiple components, somefunctionalities may, for example, be executed by a different processor230 within network device 200 than other functionalities.

FIG. 3 shows PLOAM reset message 300 according to an embodiment of thepresent disclosure. A number of the fields of PLOAM reset message 300are common to PLOAM messages and are defined by ITU-T G.989.3. PLOAMreset message 300 in the embodiment shown includes ONU-ID 301, MessageType ID 302, Sequence Number 303, Reset Scope 304, Reset Level 305,Vendor ID 306, Vendor-Specific Serial Number (VSSN) 307, Padding 308,and Message Integrity Check (MIC) 309. ONU-ID 301 includes six reservedbits, plus an actual 10-bit ONU identifier that specifies the messagerecipient in the downstream direction or the message sender in theupstream direction. Message Type ID 302 indicates the type of themessage and defines the semantics of the message payload. Forembodiments of the present disclosure, a new Message Type ID 302 valuemay be assigned for the PLOAM reset message 300. Sequence Number 303contains a sequence number counter that is used to ensure robustness ofthe PLOAM messaging channel. Vendor ID 306 is the first of twocomponents of the ONU serial number; its values are assigned by theAlliance for Telecommunications Industry Solutions. VSSN(vendor-specific serial number) 307 is the second of the two componentsof the ONU serial number; its values are selected by ONU vendors.Padding 308 may be unused, or may be defined and used for additionalinformation. MIC (message integrity check) 309 is used to verify thesender's identity and to prevent a forged PLOAM message attack. In somePLOAM messages, ONU-ID 301 may be used to identify a particular ONU, andin such messages, Vendor ID 306 and VSSN 307 may be zeroes or simplyignored by the receiver. However, because ONU IDs are assigned when anONU restarts, an OLT may need to send a message to an ONU before it hasbeen assigned an ONU ID. In such cases ONU-ID 301 of PLOAM reset message300 may be set to 0x03FF (indicating “broadcast” mode) and Vendor ID 306and VSSN 307 identify the specific ONU. By way of example and notlimitation, PLOAM reset message 300 may be sent to an ONU which has hungbefore completing normal startup, in which case ONU-ID 301 will be setto broadcast mode and Vendor ID 306 and VSSN 307 will identify thespecific ONU to be reset.

In some embodiments of PLOAM reset message 300, Reset Scope 304 may beused to identify a specific ONU or a set of ONUs to be reset. ResetScope 304 can reset the ONU having the serial number as indicated byVender ID 306 and VSSN 307. Reset Scope 304 can reset all ONUs in thePON which are in operation states 2 (“standby state”) or 3 (“serialnumber state) (Vendor ID 306 and VSSN 307 are ignored). Or, Reset Scope304 can reset all ONUs in the PON irrespective of their operation states(Vendor ID 306 and VSSN 307 are ignored). Operation states for ONUs,including the standby state and serial number states are defined byRecommendation ITU-T G.989.3.

In some embodiments of PLOAM reset message 300, Reset Level 305indicates the “depth” of the reset of the ONU (or ONUs). By way ofexample and not limitation, Reset Level 305 may indicate a request toreset some or all of the ONU's components, include any of the followinglevels. Reset Level 305 can reboot the hardware, low-level software (forexample, media access control (MAC) layer functionality), andhigher-level software (for example, the ONU configuration software).This is effectively a “cold restart,” which will result in a reset ofall of the physical hardware as well as a reset of the MAC and ONUconfigurations. Reset Level 305 can reboot the low-level andhigher-level software, which will result in a reset of the MAC and ONUconfigurations. Reset Level 305 can reboot the higher-level software,which will result in a reset of the ONU configuration. Or, Reset Level305 can reset the MAC configuration without rebooting the low-level orhigher-level software. Barring unforeseen problems with the ONU,rebooting the ONU will ultimately take the ONU(s) to the “initial state”where it may begin its normal startup procedures as described in ITU-TG.984.3.

One of ordinary skill will recognize that PLOAM reset message 300 may bemodified without departing from the spirit of the present disclosure. Byway of example and not limitation, in some embodiments, the resetmessage could include a flag of whether or not to preserve the currentMIB, so that after a reset, the ONU may either restore the MIB or elsereset the MIB to an initial configuration. Such a flag may beincorporated into Reset Scope 304, Reset Level 305, or it may be adedicated field defined in Padding 308. Further, any agreed-upon valuesmay be used to indicate Reset Scope 304 and Reset Level 305. Further,the size and ordering of various fields may be modified and additionalmessage fields may be used to indicate other reset-related features.

Some service providers may develop procedures according to theflexibility provided by the multi-level reset level. By way of exampleand not limitation, a service provider's standard procedures may be forthe OLT to send a first message that instructs the ONU to reset only itshigh-level software in order to limit disruption to a customer'sservice. Then, if the ONU fails to respond, the OLT may send PLOAM resetmessages with successively deeper ONU reset levels, and ultimatelyinstruct the ONU to perform a cold restart. For other service providers,the standard procedure for a hung ONU may always entail a cold restart.

FIG. 4 discloses flowchart 400 showing how an OLT may make use of thePLOAM reset message. In operation 401, OLT 110 detects that ONU 120 isnot responsive to OMCI messages and should be restarted using PLOAMreset message 300.

In operation 402, OLT 110 first determines whether or not an ONU ID hasbeen assigned to ONU 120. Typically, an OLT assigns ONU IDs to thoseONUs under its control, so OLT 110 should have a record of the ONU IDassigned to ONU 120. Thus, if it has assigned an ONU ID, in operation403 OLT 110 sets ONU ID 301 of PLOAM reset message 300 to the ONU ID forONU 120. Otherwise in operation 404 OLT 110 sets ONU ID 301 forbroadcast mode, and sets Vendor ID 306 and VSSN 307 of PLOAM resetmessage 300 to the vendor ID and VSSN for ONU 120, as previouslydiscussed.

Next, in operation 405, OLT 110 determines if there are reset levelsavailable for PLOAM reset message 300. The reset level chosen by OLT 110may depend on OLT 110's analysis of the problem(s) being experienced byONU 120, any PLOAM reset message 300 that OLT 110 has previously sent toONU 120, and the service provider's troubleshooting procedures. By wayof example and not limitation, OLT 110 may first attempt to reset theMAC data on ONU 120 and OLT 110, then it may attempt to reboot thehigh-level software, then it may attempt to reboot the low-levelsoftware, and finally, it may attempt a cold restart by instructing ONU120 to cycle its power.

In operation 406, OLT 110 fills in Reset Level 305 of PLOAM resetmessage 300 and in operation 407 sends the message to ONU 120. In somevariations of this embodiment, OLT 110 may also set a flag in PLOAMreset message 300 to instruct OLT 110 either to retain or discard someor all of its MIB.

In operation 408, OLT 110 determines whether or not ONU 120 hassuccessfully restarted and is operating normally. If so, then OLT 110may be finished with flowchart 400. If not, then OLT 110 may return tooperation 405 to determine if lower-level Reset Levels are appropriate.If lower-level Reset Levels are available, then OLT 110 may repeatoperations 406-408. If all reset attempts have failed, including a powercycle, then OLT 110 may exit, leaving ONU 120 non-operational, in whichcase ONU 120 may require manual attention by the service provider.

One of ordinary skill in the art will recognize a number of variationsin the implementation of the embodiment of flowchart 400. By way ofexample and not limitation, as noted previously, PLOAM reset message 300may be structured as shown in FIG. 3, while in other embodiments, thesize and ordering of various fields may be modified and additionalmessage fields may be used to indicate other reset-related features.Further, a given service provider operating ONU 120 may empiricallydetermine that certain ONU models may not respond to a first PLOAM resetmessage at a given level, but may respond to a second or third PLOAMreset message at the same reset level; thus, flowchart 400 may bemodified to repeat operations 405-408 multiple times using the samereset level. Further, a given service provider operating ONU 120 maydetermine that certain ONU models seldom respond to a simple restart ofthe higher-level software and usually require a cold restart. Thus, foroperation 406, the reset level may always be set to cold restart.Further, ONU 120 may require different amounts of time to restartdepending on Reset Level 305, so there may be a variable-length delayperiod inserted between operations 407 and 408. Further, afterdetermining that ONU 120 is operational in operation 408, OLT 110 maysend OMCI messages to ONU 120 to initiate diagnostics, retrieve errorlogs, and other tasks to verify that ONU 120 is fully operational.Further in operation 401, OLT 110 may automatically detect that ONU 120is non-responsive, for example, through the use of “keep-alive”messages. In other variations, the service provider operating OLT 110may initiate flowchart 400 manually after receiving a service requestfrom a customer. Further, if OLT 110 makes multiple attempts to resetONU 120 using ONU 120's assigned ONU ID (set in message 300 in operation403), it may repeat the attempts using broadcast mode for ONU-ID 301 andset Vendor ID 306 and VSSN 307 accordingly.

FIG. 5 shows an embodiment of processing by ONU 120 in receipt of PLOAMreset message 300 sent by OLT 110. In operation 501 of flowchart 500,ONU 120 receives PLOAM reset message 300.

In operation 502, ONU 120 examines PLOAM reset message 300 to determineif it is directed to ONU 120. As noted previously, ONU ID 301 field mayhave an ONU ID matching ONU 120's ID. Alternatively, the ONU field mayindicate broadcast mode, in which case ONU 120 must examine the VendorID and VSSN fields to determine if the message is directed to ONU 120.If the message is not directed to ONU 120, then PLOAM reset message 300is ignored and processing ends. Otherwise, processing moves forward tooperation 503 where ONU 120 examines Reset Level 305.

In operation 503, ONU 120 determines if a cold restart has beenrequested. If so, then in operation 504, ONU performs a cold restart.Depending on the hardware and software configuration of ONU 120, thismay involve cycling the power of ONU 120 or it may involve sending resetsignals to all of the electrical components of ONU 120. In either case,ONU 120 may then begin its normal startup sequence as defined byRecommendation ITU-T G.989.3.

In operation 505, ONU 120 determines if a reset of the low-level andhigh-level software has been requested. If so, then in operation 506,ONU 120 resets the low-level and high-level software. Depending on thehardware and software configuration of ONU 120, this may involveterminating individual programs and/or program groups, and/or restartingall or part of the operating system, and ONU 120 may then begin itsnormal startup sequence as defined by Recommendation ITU-T G.989.3.

In operation 507, ONU 120 determines if a reset of the high-levelsoftware has been requested. If so, then in operation 508, ONU 120resets the high-level software. Depending on the hardware and softwareconfiguration of ONU 120, this may involve terminating individualprograms and/or program groups, however, not all functionality of ONU120 may be terminated, and ONU 120 may or may not go through its normalstartup sequence as defined by Recommendation ITU-T G.989.3.

In operation 509, ONU 120 determines if a MAC reset has been requested.If so, then in operation 510, ONU 120 resets its MAC data but may nototherwise terminate or restart programs.

One of ordinary skill in the art will recognize a number of variationsin the implementation of the embodiment of flowchart 500. By way ofexample and not limitation, as noted previously, PLOAM reset message 300may be structured as shown in FIG. 3, while in other embodiments, thesize and ordering of various fields may be modified and additionalmessage fields may be used to indicate other reset-related features.Further, in some variations, ONU 120 may reset according to Reset Level305 immediately upon receipt of PLOAM reset message 300, while in othervariations, it may perform housekeeping chores, event logging, and suchbefore resetting. In some variations, ONU 120 may defer resetting untilany in-progress sessions, operations, or data transfers (such astelephone calls, for example) have been completed. In some variations,prior to restarting, ONU 120 may store its MIB tables and then afterrestarting, reload the stored MIB tables, while in other variations, ONU120 may clear its MIB tables on restart. In some variations, thedecision of whether or not to restore MIB tables may be indicated by aflag in PLOAM reset message 300.

Thus disclosed herein is a means for an ONU to store a MIB, low-levelsoftware, and high-level software, a means for the ONU to communicateusing PLOAM messages, and a means for the ONU to execute the low-levelsoftware and high-level software, receive a PLOAM reset messagecomprising a reset level with the reset level comprising an indicationof a component of the ONU to be reset, and reset the ONU according tothe reset level. Further disclosed herein is a means for an ONU toreceive a PLOAM reset message comprising a reset level, wherein thereset level comprises an indication of a component of the ONU to bereset, and a means to reset the ONU according to the reset level.Further disclosed herein is a means for an OLT to store identity andstate information about an ONU, a means for the OLT to communicate withthe ONU using PLOAM messages, a means to create a first PLOAM resetmessage, wherein the first PLOAM reset message comprises a first resetlevel and wherein the first reset level comprises an indication of acomponent of the ONU to be reset, and a means to send the first PLOAMreset message to the ONU. Further disclosed herein is a means for an OLTto create a first PLOAM reset message, wherein the first PLOAM resetmessage comprises a first reset level, wherein the first reset levelcomprises an indication of a component of the ONU to be reset, and ameans to send the first PLOAM reset message to the ONU via a PLOAMchannel.

Although the present disclosure has been described with reference tospecific features and embodiments thereof, it is evident that variousmodifications and combinations can be made thereto without departingfrom scope of the disclosure. The specification and drawings are,accordingly, to be regarded simply as an illustration of the disclosureas defined by the appended claims, and are contemplated to cover any andall modifications, variations, combinations or equivalents that fallwithin the scope of the present disclosure.

What is claimed is:
 1. A method for an optical network unit (ONU)comprising high-level software to receive and process a physical layeroperations, administration, and maintenance (PLOAM) reset message, themethod comprising: receiving the PLOAM reset message comprising a resetlevel and with the reset level comprising an indication of a componentof the ONU to be reset and an instruction to reset the high-levelsoftware; and resetting the component of the ONU and the high-levelsoftware according to the reset level.
 2. The method of claim 1, whereinthe ONU comprises hardware and low-level software, wherein the resetlevel comprises an instruction for the ONU to reset the hardware and thelow-level software, and with the method further comprising resetting thehardware and the low-level software.
 3. The method of claim 1, whereinthe ONU comprises low-level software, wherein the reset level comprisesan instruction for the ONU to reset the low-level software, and with themethod further comprising resetting the low-level software.
 4. Themethod of claim 1, wherein the ONU comprises a management informationbase (MIB), wherein the reset level comprises an instruction for the ONUto reset the MIB, and with the method further comprising resetting theMIB.
 5. The method of claim 1, wherein the ONU comprises a managementinformation base (MIB), wherein the PLOAM reset message furthercomprises an instruction for the ONU to preserve the MIB beforeresetting the ONU, and with the method further comprising: preservingthe MIB before resetting the ONU; and restoring the MIB after resettingthe ONU.
 6. The method of claim 1, wherein the ONU comprises a currentoperating state, wherein the PLOAM reset message further comprises aconditional reset instruction or an unconditional reset instruction,wherein the conditional reset instruction comprises an indicator of anONU operating state, and with the method further comprising: resettingthe ONU when the PLOAM reset message comprises the conditional resetinstruction and when the current operating state corresponds to theindicator of the ONU operating state; and resetting the ONU when thePLOAM reset message comprises the unconditional reset instruction.
 7. Amethod for an optical line terminal (OLT) to reset a remote opticalnetwork unit (ONU) comprising high-level software, the methodcomprising: creating a first physical layer operations, administration,and maintenance (PLOAM) reset message comprising a first reset level,with the first reset level comprising an indication of a component ofthe ONU to be reset and an instruction to reset the high-level software;and sending the first PLOAM reset message to the ONU via a PLOAMchannel, the first PLOAM reset message instructing the ONU to reset thecomponent and the high-level software according to the reset level. 8.The method of claim 7, wherein the first reset level comprises aninstruction for the ONU to reset hardware and low-level softwareassociated with the ONU, an instruction for the ONU to reset low-levelsoftware associated with the ONU, or an instruction for the ONU to reseta management information base (MIB) associated with the ONU.
 9. Themethod of claim 7, wherein prior to creating the first PLOAM resetmessage, the method further comprises detecting that the ONU is notresponding to optical network terminal management and control interface(OMCI) messages and wherein after sending the first PLOAM reset message,the method further comprises: detecting that the ONU is still notresponding to OMCI messages; creating a second PLOAM reset messagecomprising a second reset level, and wherein the second reset level isdifferent from the first reset level; and sending the second PLOAM resetmessage to the ONU via the PLOAM channel.